Field of the Invention
The present invention relates to a method of dressing a honing wheel which is brought into contact with a dressing tool carried on a gear cutting machine.
For the purpose of ensuring highly precise geometry of gear teeth to be used in various applications including automobiles, the gear teeth are subjected to a honing finish step alter completing a gear cutting operation with a gear cutting machine. The conventional gear cutting machine incorporating a honing wheel is sold under the trade name of Fassler D-250-C. This has a construction such as that shown in FIG. 1 wherein a gear 4 to be finished is arranged between a head stock 31 and a tail stock 32 on a worktable 3 in such a manner that an axis of head stock 31 is co-linear with an axis of the tail stock 32 and the gear 4 is rotatably carried on both centers 41, 42. A honing wheel 1 is at an incline arranged with respect to the axis of stocks 31, 32, and at an inclination angle .theta.. Honing wheel 1 can be rotated by a power source to permit the honing of gear teeth (not shown) of a gear 4 carried on the stocks 31, 32 as will be explained further below in connection with the embodiment of the present invention.
For the honing finish operation of the gear teeth (not shown) by means of the honing wheel 1, a hone (not shown) is secured to an inner surface of honing wheel 1. The hone (not shown) and honing wheel 1 are brought into contact with the gear 4 until for example a total honing in-feed, i.e., distance of travel, amounts to 1-2 .mu.m while the honing wheel 1 is rotated and fed against gear 4. The hone (not shown) becomes considerably worn after the honing finish operation of a large number of the gears 4, and eventually highly precise gear teeth cannot be obtained using that hone.
After considerable wear of the hone beyond a predetermined amount, the honing wheel 1 must be provided with a replacement hone (not shown). However, a new hone (not shown) may not be satisfactory in the accuracy of its size. Consequently, a dressing, i.e., sizing operation, is required to precisely size the new hone (not shown).
The dressing operation is performed by a dressing ring 5 which serves to dress an inner surface (not shown) of the hone (not shown) and a dressing gear 6 which serves to dress the surfaces of the hone (not shown) corresponding to the gear teeth (not shown) of the gear 4 (refer to FIGS. 2 and 6). A conventional method of dressing a hone is composed of the following steps.
The steps of the dressing the new hone (not shown) in the honing wheel 1 using the dressing 5 and the dressing gear 6 collectively as a dressing tool 5 or 6 are illustrated in FIGS. 2 and 6. A spindle 15 with the ring 5 is substituted for the gear 4 between both the centers 41, 42 and the worktable 3 is reciprocally traversed along a bed so as to locate the ring 5 inside the honing wheel 1. Referring to FIGS. 4 and 5, the inner surface (not shown) of the hone (not shown) in the honing wheel 1 is brought into contact with the dressing ring 5 to dress the inner surface (not shown) of the hone (not shown) by rotating the honing wheel 1 and feeding dressing tool 5 or 6 against the inner surface of the honing wheel 1.
Referring to FIG. 11, individual in-feed and transverse feed steps for dressing the honing wheel 1 and the dressing ring 5 are illustrated. At each end of the transverse feed stroke of the worktable 3, the in-feed step of honing wheel 1 toward and against dressing ring 5 is carried out. For example, if a total dressing in-feed is 2.5 .mu.m, five individual in-feeding steps for each 0.5 .mu.m are performed. It is noted that in this approach, constant in-feed steps of small values are employed. After dressing the inner surface of the hone in the honing wheel 1, and as shown in FIGS. 6 and 7, a spindle 16 with the dressing gear 6 is substituted for the spindle 15 on the worktable 3 for the purpose of dressing the surfaces of the hone corresponding to gear teeth of the gear 4 to be honed. The in-feed steps, when moving honing wheel 1 against dressing gear 6, are carried out in the same manner as the steps for in-feeding the dressing ring 5 as mentioned above, namely, the in-feeding of the honing wheel 1 to the dressing gear 6 is subdivided into several individual in-feed steps in which honing wheel 1 moves in constant, small distances (see FIG. 11).
The completion of the dressing of the honing wheel 1 will lead to the honing finish operation of a new work, namely, gear 4 (refer to FIGS. 8 and 9).
This conventional approach to dressing the hone in the honing wheel 1 is based on the concept that the in-feeding of honing wheel 1 toward the dressing ring 5 or dressing gear 6 is subdivided into several individual in-feed steps by moving honing wheel 1 a constant small distance at the end of each transverse stroke of the dressing tool 5 or 6. In order to prevent the breaking of the hone (not shown) in the honing wheel 1, the amount of each in-feed is limited to a small value, for example, a value of 0.5 .mu.m, which is smaller than a maximum permissible value of the elastic deformation of a hone (not shown) to be dressed. Because of the relatively small distance moved by honing wheel 1 during each in-feed step, the previously described conventional approach results in a large number of reciprocal movements of the dressing tool 5 or 6, and prolongs the working time required to dress a honing wheel 1.